Method of making coke from hydrocarbon residues



Jlme 25. 1940. A. P'. SACHS 2,205,631

. METHOD 0F MAKING CQKE FROM HYDROCARBON RESIDUES Filed July 6, 1938 aan179// $99 INVENTORv Az 55e 7' P Snr/#.5

M01/17 ATTORNEY Y Patented June 25, 1940 UNITED STATES METHOD or MAKINGCOKE FROM HYDRocARBoN RESIDUES Albert P. Sachs, New York, N. Y.,assignor to Petroleum Conversion Corporation, Elizabeth, N. J., acorporation of Delaware Application July 6, 1938, Serial No. 217,670

4 Claims.

My present invention relates to improvements in the art of coking heavyhydrocarbon oil, especially the residues from oil cracking systems. Themain object of the invention is to produce 5 coke extremely low in orsubstantially free from volatile lnatter.

In carrying out my invention in its preferred embodiment I introduce acharge of oil to be coked. which preferably has been suitably freed fromlighter components, into the coking vessel to ll the same to a fractiononly of the height of the coking vessel, whereupon I bring about cokingof the charge preferably by introducing into the body thereof a heatednon-liquid, fluid heat carrying medium, e. g., hydrocarbon or otherinert gas or hot hydrocarbon vapors from a cracking or reformingoperation. After the initial charge in the coking vessel has been thuscoked, the supply of heating medium is stoppecLvor at least greatlydiminished, and the contents of the coking vessel subjected to theaction of a relatively high vacuum to thereby remove volatile matters inthe coke. After the desired effect has been had by the action of thevacuum, the vacuum pump,

steam vacuum jet or other means of producing the vacuum is cut off, theheat carrier admitted for a short time to warm up the residual coke,whereupon a fresh supply of oil to be coked is charged above the cokebody and the coking operation continued. In this manner the charge ofcoke in the vessel is gradually built up while subject to vacuum actionas each increment of coke is formed.

The invention will be best understood by reference tothe followingdetailed description taken with the accompanying,drawing. the singlefig- -ure of which shows diagrammatically a plant embodying a preferredform of the invention.

For the sake of illustration the invention is shown in connection with atype of cracking process, known in the art as the TVP process, althoughresidual oils from other sources may be used, and the present cokingoperation maybe used in connection with any type of cracking process.De-

scribing first the cracking system, cracking stock is admitted tovaporizer I through pipe 2 wherein it is heated and subjected to ashvaporization in the flash drum 3, being admittedl thereto through pipe4. The released vapor leaves the drum 3 through pipe 5 through which itis conducted to a superheater 6. The superheated vapor leaves the heater6 through pipe 1 by which it is conducted to reaction chamber 8. At' thesame time a gaseous heat carrier, as for example the residual gas of thecracking system, is heated up in the furnace 9 tov a temperaturesomewhat higher than that of the vapors from superheater 6, is conductedfrom furnace 9 through pipe I0 and mingles with the vapors in pipe 1,the mixture of gas and vapors thereupon being admitted to 5 the reactionchamber 8. 'I'he vapors become cracked' in said reaction chamber and themixture of the gas and cracked vapor leaves the same through pipe I I bywhich it is conducted to fractionator I2. In said fractionator thecracked 10 products are separated into an overhead fraction containingthe gasoline vapors which leaves through pipe I3 and is subjected tovarious recovery and refining treatments usual in the art, by means notshown, and a bottoms fraction which is 16 withdrawn through pipe I4.Various intermediate fractions `are also produced including a recyclestock which it is not necessary to describe, and the fractionator isreuxed as is usual in the art, but the means therefor are not shown. 20

The residue to be coked leavingthrough pipe I4 is preferably subjectedto the stripping action, at a pressure lower than the fractionatorpressure of an atmospheric stripping tower or flash drum I5 (thepressure obtaining in the fractionator 25 being, say, of the order of 50to 100 pounds per square inch gage) wherein the overhead of lightervapors is produced. leaving through pipe I6, passing through condenserI'I communicating with which is accumulator I8. The condensed distillatecollecting in I8 may be used. as recycle stock or for other purposes.The stripped residue, say, by way of example, of a gravity of '7 or 8 A.P. I., leaves the stripper I5 through pipe 20 by means of which itpasses to coking vessel 2l. 35

yPipe 20 Amay be provided' with a pump not shown or the ow of strippedresidue may be carried out by the difference in pressure, coking chamber2| being operated at a lower pressure than flash tower I5. Preferablypipe 20 has a plurality of valved 40 connections or inlets 22a, 22h,etc., to the drum 2| spaced throughout substantially the height thereof,by means of which the oil to be coked can be introduced at differentlevels of the drum. For example, in a drum 20 feet high the inlets 22 45may be at two-foot intervals. -Although one inlet at the top may besuicient, a plurality of inlets is provided to guard against the dangerof the coking up of that one'inlet. Heated gas or hot products from acracking or reforming operation 50 from a source not shown areintroduced into the drum 2| through pipe 23 and any one of spacedvalveconneetions 24a, 2lb, etc., as may be desired.

At the start of the coking operation a measured amount of oil isadmitted to the drum2l, r

by valve 22a or any other convenient inlet sufficient to give a cokecharge of a height not exceeding the second inlet connection 22h. Hotgas or other coking medium is then admitted from pipe 23 throughconnection 24a for a sufcient time to bring about coking of the charge,the overhead products leaving the drum 2| through pipe 25, vthroughwhich they pass to a condenser 26 in communication with which is anaccumulator 21 for condensate, the residual gas being removed throughpipe 28 to a disposition not shown. Where hot cracked vapors areemployed as the coking medium the overhead products may be led offthrough branch pipe 25a back to the fractionator 2 or may be condensedin 26, accumulated as liquid in 21 and pumped to any part of the systemas desired. .When the charge has been coked the admission of gas orvapor through pipe 23 tothe coking vessel 2| is either shut oif orclosed down so that only a slight quantity is admitted. The vacuum pump30 having been started is placed in communication with the drum 2|through pipe 3| having therein valve 32, accumulator 21, condenser 26,pipe 25, pipe 28 being closed off by means of valve 28a. Branch line 25ais likewise valve olf. The action of the vacuum is to removesubstantially all of the volatile content of the charge of coke formed,after which line 3| to the pump is closed off by closing valve 32. thecoke charge preferably warmed by admitting some of the hot gas to thedrum 2|, whereupon valve 22h, or any higher inlet valve, is opened and afresh charge of residue oil admitted, and a second layer of coke isbuilt up and again subjected to the action of vacuum, in a manneralready described, the process being repeated until the capacity of thedrum 2| is reached, making use of the valve connections 22a, 22h, 22e,22d, etc. A plurality of gas connections 24a, 24h, 24e, 24d, etc., isalso provided, should it be necessary to add the gas higher in the drum2| as the formation of coke progresses. If, as mentioned, a slightamount of the coking medium, gas or hot vapors, etc., is admitted duringthe vacuum operation, the stripping operation of the volatiles isfacilitated. Steam may also be used to carry out the strippingoperation, and if desired steam preferably superheated may be used asthe heating medium in the coking operation.

When the capacity of drum 2| for coke has been reached, the entirecharge is removed in the usual manner and, if necessary, the coking iscontinued in one or more other coking drums similar to 2|.

Various changes in the method above given in detail will occur to thoseskilled in the art, Without departing from the spirit of my invention orthe scope of the appended claims.

I claim:

1. In a system of cracking hydrocarbon oils in which the oil iscrackedin the vapor phase in a reaction chamber and the products therefrom arewithdrawn and passed to a zone of fractionation, the method of handlingthe residue from the fractionation zone which comprises the steps ofpassing a charge of bottoms therefrom to a coking vessel to yield a cokelayer which will be a fraction only of the capacity of such vessel andbuilding up therein a layer of coke by passing through said charge hotcracked vapors from a further cracking operation, withdrawing from thecoking vessel the hot cracked products admixed with vapors produced inthe coking operation and passing such admixture back to thefractionating zone and admitting same thereto at a point above thewithdrawal of thc bottoms. subjecting the coke so formed to the actionof vacuum to remove therefrom volatile matter in the coke, discontinuingthe vacuum action, adding a fresh charge to the devolatilized coke soformed and continuing the stated operations of coke formation anddevolatilization until a predetermined depth of coke is built up.

2. 'I'he method of coking which comprises the steps of depositing a cokeyielding hydrocarbon in a vessel to a fraction of the depth thereof toyield a comparatively thin layer of coke such that upon subsequentapplication of vacuum the coking layer formed will be readilydevolatilized, coking the hydrocarbon so deposited, then applying vacuumthereto to devolatilize the same, discontinuing said vacuum when thedevolatilization is substantially completed, thereafter adding a freshcharge of said hydrocarbon to the devolatilized coke so formed andcontinuing the operations of coke formation and devolatilization asaforesaid to build up stepwise a predetermined depth of coke in thevessel.

3. The method according to claim 2, in which the coking is brought aboutby the action of a substantially inert heated non-hydrocarbon liquidwhich is passed through the hydrocarbon to be coked.

4. The method according to claim 2 in which a reduced stream of heatingfluid issupplied to the coking vessel during the vacuum action topromote the removal of volatile matter.

ALBERT P. SACHS.

